According to previous studies, presence of high proportion of dense (fibroglandular) breast tissue as a mammographic density is an identifiable risk factor for occurrence of breast cancer. However, the possible link between non-dense or fat tissue and breast cancer risk still remains unclear.
New research published in BioMed Central’s open access journal Breast Cancer Research reported that the breast cancer risk is associated with both dense (fibroglandular tissue) and non-dense (fat) tissue, and shows that large areas of either are independently associated with an increased risk. Interestingly, breast cancer risk with large area of fat tissue remains same even after taking BMI into account.
In the present case-control study, researchers from the University Medical Centre Utrecht enrolled 1700 post-menopausal, Caucasian, women aged between 49 to 70 years. Current breast cancer cases from selected cohort were identified from regional cancer registry. Proportion of three controls for each breast cancer case was selected from the cohort.Both cases and controls were free from any other type of cancer, except non-melanoma skin cancer and breast implants at enrolment point. Cases were excluded if previously they had less than 3 mammograms, which was a pre-requisite for a study to note changes in mammographic density or if the previous mammogram could not be recollected.
Researchers analysed and compared the mammographic films of women with breast cancer to women who did not have cancer. The study used advanced computer software for evaluating the mammographic density, so to eliminate error in reading film reports. The software compared the proportion of dense tissue with non-dense tissue and was not look for definite irregularities.Reader set two thresholds to read films; one to distinguish the breast area from the background and a second to distinguish the dense from the non-dense area.
As usual, the percentage of non-dense tissue is higher in older women and women with a higher BMI. Breast cancer risk is significantly observed higher in women with a large area of dense tissue and a small area of non-dense tissue than with a small area of both tissue types. Women with breast cancer are inclined to have large areas of dense and non-dense tissue, so highest risk was for women with the largest areas of both.
However findings were not statistically significant in consideration with breast size because risk of cancer related with fat though significant is not as high as with dense tissue. Also size of breast was not indicative of amount of dense or non-dense tissue and hence did not necessarily have a higher breast cancer risk.
[box type=”important”]According to researchers, fat cells are considered as highly active endocrine cells that secrete numerous hormones which thought to play important role in breast cancer etiology. More researches are still needed to know, exactly how fat tissue can raise breast cancer risk. [/box]
Dr Carla van Gils, from the University Medical Centre Utrecht, who lead the research explained:
“Fat tissue is known to produce the hormones such as oestrogen which are known to promote the growth of ER positive cancer. However it seems that it is the local fat tissue which is important to breast cancer risk at not just general body fat (as measured using BMI). Consequently it may be important to consider both types of tissue when assessing breast cancer risk.”